Cheap RF Wireless Between Arduinos

Forum 2005-2010 (read only) General Exhibition
1

I was looking for a way to handle wireless communications between two Arduino boards. Other options like Xbee or Bluetooth were going to cost $50 to over $100. Then I found a cheap RF transmitter and receiver at Sparkfun. The total cost is only $9!

For a full description and all the code check out this writeup. http://www.glacialwanderer.com/hobbyrobotics/?p=291

Here's the circuit I used.

768×768 105 KB

And some of the code:

// Sends an unsigned int over the RF network
void writeUInt(unsigned int val)
{
  byte checksum = (val/256) ^ (val&0xFF);
  Serial.write(0xF0);  // This gets reciever in sync with transmitter
  Serial.write(g_network_sig, NETWORK_SIG_SIZE);
  Serial.write((byte*)&val, VAL_SIZE);
  Serial.write(checksum); //CHECKSUM_SIZE
}

// Receives an unsigned int over the RF network
unsigned int readUInt(bool wait)
{
  int pos = 0;          // Position in the network signature
  unsigned int val;     // Value of the unsigned int
  byte c = 0;           // Current byte
  
  if((Serial.available() < PACKET_SIZE) && (wait == false))
  {
    return 0xFFFF;
  }
  
  while(pos < NETWORK_SIG_SIZE)
  { 
    while(Serial.available() == 0); // Wait until something is avalible
    c = Serial.read();

    if (c == g_network_sig[pos])
    {
      if (pos == NETWORK_SIG_SIZE-1)
      {
        byte checksum;

        while(Serial.available() < VAL_SIZE + CHECKSUM_SIZE); // Wait until something is avalible
        val      =  Serial.read();
        val      += ((unsigned int)Serial.read())*256;
        checksum =  Serial.read();
        
        if (checksum != ((val/256) ^ (val&0xFF)))
        {
          // Checksum failed
          pos = -1;
        }
      }
      ++pos;
    }
    else if (c == g_network_sig[0])
    {
      pos = 1;
    }
    else
    {
      pos = 0;
      if (!wait)
      {
        return 0xFFFF;
      }
    }
  }
  return val;
}

For a full description and all the code check out this writeup. http://www.glacialwanderer.com/hobbyrobotics/?p=291

2

I believe you can also use the VirtualWire library with these modules. I know it works for the 433 MHz modules from Sparkfun.

3

That is an amazing price compared to Xbee and Bluetooth! Thanks for letting us know.

4

Veronica, that VirtualWire library looks like it would work. It seemed to be pretty nice, but I didn't see an option to use the hardware UART (hardware serial support on pins 0/1). Did I miss this? If you're using the UART for for other things this looks like it might be a nice library, but using the hardware UART would give big advantages like using less cycles and having a built in buffer that you don't need to constantly watch with the receiver.

5

I've been working on this exact concept for a little while now. I've build a protocol which sits ontop of the reliable VirtualWire library.

http://milesburton.com/wiki/index.php?title=HyperCom_Packet_Library

It's been quite an interesting project so far. I've setup two protocol radios so allow half-duplex, two way communication between arduinos.

THe only bad aspect of these radios is speed. You cannot tranfer much data, reliably.

6

To be honest, I've only used it for one project, as a cheap replacement for a broken tx/rx in an rc car.

I know you can set which pins to use as rx/tx but I just used the defaults. Not sure what would happen if you used 0/1 of the arduino.

Ver

7

You could use 0,1 if you wanted. I'd avoid it just incase you get some kind of conflicts

Some media:

There's a slight bug with the transmitter but you can see it all working here:

I honestly think these little radios are the way forward for cheap long distance. If you throw in a small controller chip to provide reliability - it would rock

8

Your enthusiasm taken to a whole new level:
http://news.jeelabs.org/